I can understand limiting the map pool in competitive and even maybe in HL on a per season type thing...... like it might be a neat idea if like HGC league or whatever it's called was like 5 specific maps and that HL season was also the same 5 maps, that could be a really cool way to help people really learn the intricacies of maps.
But in QM and unranked the maps are fine, new HM is about 6 million times better then the old one, and none of the maps are very complicated..... go to the flashy icon and do the thing is all new or returning players need to know. There's really nothing sophisticated about them that has significant impact on QM outcome.... like the outcome of QM games is something yo be concerned about anyway. even things like what is the better solo lane is kind of irrelevant outside of draft modes really.
i feel like the biggest learning curve for new players is xp mechanics and of course the heroes. I haven't bothered to check out the new player experience in a very long time, but they don't explain xp anywhere as far as I know.
That being said I wouldn't mind if they removed curse, dk, booty bay, and garden to significantly rework them like they did for haunted mines. Not that they need it as bad, but they just so damn generic at this point that they kind of aren't as much fun to play on as the new diablo and Starcraft maps. They should full commit to make them Warcraft maps and give them an art and mechanics pass.